For the past 15 years, excessive keratansulfaturia in patients with radiographic evidence of osteochondrodystrophy has allowed the general diagnosis of Morquio disease (MPSose IV). More recently, specific enzyme measurements have demonstrated the existence of at least three different diseases secondary to defective degradation of keratan sulfate: Morquio A (galactose, or N-acetylgalactosamine-6-sulfate sulfatase deficiency); Morquio B (beta-galactosidase deficiency); and MPSosis VIII (N-acetylglucosamine-6-sulfate sulfatase deficiency). Despite these improved diagnostic capabilities, there are still many patients with osteochondrodystrophy and keratansulfaturia who do not fit in the above categories. The structure of the repeating unit of keratan sulfate suggests that some of those unclassified patients might have a deficiency of the enzyme beta-N-acetylglucosaminidase. A storage disease secondary to deficiency of this enzyme has not been described and, in fact, there is not a method available for its measurement. Objective of our research is a o prepare the disaccharid N-acetylglucosamine beta-1 yields 3-D-galactose from shark keratan sulfate by enzymic degradation and chemical desulfation; b) to reduce it with NaB3H4 to the corresponding 1-3H-galacititol; c) to use this radioactive substrate for the measurement of beta-N-acetylglucosaminidase. For this purpose we shall use cultured skin fibroblasts of patients with keratansulfaturia who have been proven to have normal activity for beta-galactosidase and the two N-acetylhexosamine-6-sulfate sulfatases.